[Ada] Assorted LTO fixes

[Ada] Assorted LTO fixes

[Eric Botcazou]

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This polishes a few rough edges visible in LTO mode.

Tested on x86-64/Linux, applied on mainline, 10 and 9 branches.


2021-02-03  Eric Botcazou  <ebotcazou@adacore.com>

	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Array_Type>: Make the
	two fields of the fat pointer type addressable, and do not make the
	template type read-only.
	<E_Record_Type>: If the type has discriminants, mark it as may_alias.
	* gcc-interface/utils.c (make_dummy_type): Likewise.
	(build_dummy_unc_pointer_types): Likewise.

-- 
Eric Botcazou

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diff --git a/gcc/ada/gcc-interface/decl.c b/gcc/ada/gcc-interface/decl.c
index 5ea1b16af67..8120d4e33cf 100644
--- a/gcc/ada/gcc-interface/decl.c
+++ b/gcc/ada/gcc-interface/decl.c
@@ -2197,14 +2197,16 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	  }
 	else
 	  {
+	    /* We make the fields addressable for the sake of compatibility
+	       with languages for which the regular fields are addressable.  */
 	    tem
 	      = create_field_decl (get_identifier ("P_ARRAY"),
 				   ptr_type_node, gnu_fat_type,
-				   NULL_TREE, NULL_TREE, 0, 0);
+				   NULL_TREE, NULL_TREE, 0, 1);
 	    DECL_CHAIN (tem)
 	      = create_field_decl (get_identifier ("P_BOUNDS"),
 				   gnu_ptr_template, gnu_fat_type,
-				   NULL_TREE, NULL_TREE, 0, 0);
+				   NULL_TREE, NULL_TREE, 0, 1);
 	    finish_fat_pointer_type (gnu_fat_type, tem);
 	    SET_TYPE_UNCONSTRAINED_ARRAY (gnu_fat_type, gnu_type);
 	  }
@@ -2327,7 +2329,6 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 	finish_record_type (gnu_template_type, gnu_template_fields, 0,
 			    debug_info_p);
 	TYPE_CONTEXT (gnu_template_type) = current_function_decl;
-	TYPE_READONLY (gnu_template_type) = 1;
 
 	/* If Component_Size is not already specified, annotate it with the
 	   size of the component.  */
@@ -3054,15 +3055,24 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
 		        || type_annotate_only);
 	  }
 
-	/* Make a node for the record.  If we are not defining the record,
-	   suppress expanding incomplete types.  */
+	/* Make a node for the record type.  */
 	gnu_type = make_node (tree_code_for_record_type (gnat_entity));
 	TYPE_NAME (gnu_type) = gnu_entity_name;
 	TYPE_PACKED (gnu_type) = (packed != 0) || has_align || has_rep;
 	TYPE_REVERSE_STORAGE_ORDER (gnu_type)
 	  = Reverse_Storage_Order (gnat_entity);
+
+	/* If the record type has discriminants, pointers to it may also point
+	   to constrained subtypes of it, so mark it as may_alias for LTO.  */
+	if (has_discr)
+	  prepend_one_attribute
+	    (&attr_list, ATTR_MACHINE_ATTRIBUTE,
+	     get_identifier ("may_alias"), NULL_TREE,
+	     gnat_entity);
+
 	process_attributes (&gnu_type, &attr_list, true, gnat_entity);
 
+	/* If we are not defining it, suppress expanding incomplete types.  */
 	if (!definition)
 	  {
 	    defer_incomplete_level++;
diff --git a/gcc/ada/gcc-interface/utils.c b/gcc/ada/gcc-interface/utils.c
index c503bfbb36d..2656f117fa9 100644
--- a/gcc/ada/gcc-interface/utils.c
+++ b/gcc/ada/gcc-interface/utils.c
@@ -467,6 +467,11 @@ make_dummy_type (Entity_Id gnat_type)
     = create_type_stub_decl (TYPE_NAME (gnu_type), gnu_type);
   if (Is_By_Reference_Type (gnat_equiv))
     TYPE_BY_REFERENCE_P (gnu_type) = 1;
+  if (Has_Discriminants (gnat_equiv))
+    decl_attributes (&gnu_type,
+		     tree_cons (get_identifier ("may_alias"), NULL_TREE,
+				NULL_TREE),
+		     ATTR_FLAG_TYPE_IN_PLACE);
 
   SET_DUMMY_NODE (gnat_equiv, gnu_type);
 
@@ -516,10 +521,10 @@ build_dummy_unc_pointer_types (Entity_Id gnat_desig_type, tree gnu_desig_type)
     = create_type_stub_decl (create_concat_name (gnat_desig_type, "XUP"),
 			     gnu_fat_type);
   fields = create_field_decl (get_identifier ("P_ARRAY"), gnu_ptr_array,
-			      gnu_fat_type, NULL_TREE, NULL_TREE, 0, 0);
+			      gnu_fat_type, NULL_TREE, NULL_TREE, 0, 1);
   DECL_CHAIN (fields)
     = create_field_decl (get_identifier ("P_BOUNDS"), gnu_ptr_template,
-			 gnu_fat_type, NULL_TREE, NULL_TREE, 0, 0);
+			 gnu_fat_type, NULL_TREE, NULL_TREE, 0, 1);
   finish_fat_pointer_type (gnu_fat_type, fields);
   SET_TYPE_UNCONSTRAINED_ARRAY (gnu_fat_type, gnu_desig_type);
   /* Suppress debug info until after the type is completed.  */